Yep, I do that too. Both to others and to myself and especially when I'm tired (when I also do a good line on insisting on doing *more* things). It's one of the beastlier aspects and I feel very ashamed.
I don't know whether it's the PD or the meds. The neuro didn't sound all that interested.
The advice i give myself a) Know this happens, even if you don't understand why. b) recognise when you're about to kick off and withdraw (easier said then done: it is indeed like flipping a switch).
The advice I give my oh is a) as above, b) acknowledge when it happens, but try not to pick a fight with me, c) understand that if I walk away it's to try to control myself.
Of course, this needs a grownup conversation between me and my oh - which we've been able to have, though others might find that hard.
Let us know how you get on.
yours in peace and harmony!